The present invention relates to a curling device preferably for cigarette making machines.
The invention finds application to advantage in the art field of cigarette making machinery, and in particular of filter tip attachments, that is to say machine units by which filters and cigarettes are assembled. Reference is made explicitly to this art field in the following specification, albeit with no limitation in general scope implied.
Conventionally, cigarettes and filter tips are assembled by interposing a double length filter plug between two axially aligned cigarette sticks, then joining the filter to the sticks on each side by applying a previously gummed tipping paper, and ultimately cutting the double assembly in half to create two single filter-and-cigarette assemblies.
A filter tip attachment generally comprises a feed station from which a continuous strip of paper material is advanced at a predetermined velocity and under a predetermined degree of tension along a feed path, likewise predetermined; the feed path passes both through a gumming station at which an adhesive substance is applied to one surface of the strip destined to engage the filter-and-cigarette assembly, and through a cutting unit by which the continuous strip is divided into discrete tipping papers ready for application.
Each tipping paper separated by the cutting unit is positioned at an intermediate transfer station and there associated initially with a respective filter-and-cigarette assembly, before being affixed permanently to the selfsame assembly at a further station. The step of affixing the tipping paper permanently to the filter-and-cigarette assembly is accomplished normally by wrapping the paper around the assembly.
This wrapping operation is much facilitated by a curling device installed between the feed station and the cutting unit, which engages the advancing strip and brings about a plastic deformation of the internal fibers. The material thus assumes a given curvature, when relieved of longitudinal tension, with the result that the application of the papers to the respective filter-and-cigarette assemblies is made easier.
The prior art embraces curling devices embodied substantially as a sharp edged element or blade, offered in contact to the continuous strip and generating an action that is designed to weaken the selfsame strip in the transverse direction.
Such curling devices betray certain drawbacks attributable principally to the friction generated at the area of contact between the strip and the aforementioned blade. In particular, it has been observed that the deforming action of the curling device generates high frictional forces tending often to degrade or to break the strip material, especially at the high operating speeds of filter tip attachments now in service.
The object of the present invention is to provide a curling device from which the drawbacks mentioned above are absent.